1. Field of the Invention
This invention relates to printer control systems and relates more particularly to control systems for multi-speed bidirectional printers.
2. Description of the Prior Art
A multi-speed bidirectional printer is a device in which a print carriage containing a printing mechanism is driven past a medium on which printing is to take place, the carriage and printing mechanism being controllable to move at different speeds on different lines and being capable of printing in both directions. In printers of this type, it is necessary to accelerate the carriage in the margin area of the medium so that it is up to the required speed when it reaches the printing area, maintain the desired speed as the carriage traverses a line in the printing area; and then decelerate the carriage for stopping or stopping and turning around at the end of the printing line. In such a system, it is important for printer throughput purposes that the acceleration and deceleration be carried out as rapidly as possible and that the speed during printing be substantially constant.
One factor which makes realization of these performance goals difficult to achieve over the life of a printer is that the printer system's dynamics often change from machine to machine and as a function of time as components wear and age. Hence, a control system which is capable of providing optimal control early in the life of a given printer may not be capable of such control later in the life of that printer or with another printer which is seemingly identical to that printer, but which has slightly different characteristics.
An additional factor which makes it difficult to attain these goals is that even at the same speed, a printer may have different characteristics depending on which direction it is running, thus making it harder to develop a control algorithm for a common printing speed.